The search for the woman described as a loving mother of four was suspended Monday night, nearly two full days after she disappeared and her husband was killed in a one-car accident.

The search is expected to pick up again at 9 a.m. Tuesday, with volunteers on foot expanding the search area.

"We're taking nothing for granted," said LaSalle County Sheriff Tom Templeton. "As long as we have the resources available, we will continue searching."

Shannon, 40, was last seen riding home from a holiday party with her husband, 41-year-old Dale Shannon, behind the wheel, authorities said.

"They were having a great time. They were dancing together, laughing and very much in love with each other," said Dale's sister, Donna Shannon.

Police on patrol found the car near Seneca, about 80 miles from Chicago, early Sunday morning. They said the car spun out and the rear of it hit a utility pole, breaking Dale Shannon's back. He was found dead behind the wheel.

Footprints that investigators believe belonged to Tanya Shannon, as well as a single shoe, were found nearby.

"Tracks coming from the driver's side door of the crashed vehicle up to the road and a shoe, it was like a slip-on shoe, was recovered," said Templeton.

A nuclear power plant is nearby, but Templeton said it doesn't appear that Shannon walked that way. If she had reached the perimeter fence, alarms would have sounded, he said.

Since Sunday, thermal imaging devices, dogs, All-Terrain Vehicles and planes have been used by dozens of people looking for her.

Investigators said they have only two working theories: that she was injured and disoriented as she went for help on the bitter cold, wind-swept road and collapsed somewhere in the snow, or that someone picked her up under the guise of offering assistance.

With repeated searches, they have all but disproved their first theory and have no leads on the second.